[1.5]KeepMyStats

Below I say that the mod is version independant and works with every Minecraft version 1.5 and up. This is true in general, but the new launcher broke the mod.

In Minecraft 1.5 the statistics system has changed and the resetting of statistics should be rare to impossible. If you want you can still use this mod, but it's way less important than before 1.5.

This mod removes the resetting of statistics and achievements.
Additionally it will make the game access the statistics file stat_keepmystats_unsent.dat (instead of stat_<username>_unsent.dat). So when you start the game without the mod installed, it won't mess up your statistics.
The mod is a FML coremod. This means it requires FML or Forge and goes into the coremods folder. It does not do any Minecraft stuff, so it should be independent of the Minecraft version. It should work with all future releases and snapshots that FML works with. You can even put it in an MCP installation in the coremods folder.
Statistics are client only. Don't install the mod on a server.

For the old versions: forget everything I just said. They are not coremods, don't require FML and don't rename the statistics file. They simply keep the game from resetting the statistics. They are version specific and need to be installed in the minecraft.jar. If you want to use the with Forge/FML, installed them after Forge/FML. Don't forget to delete the META-INF folder.Downloads

Many people play Minecraft. Many people use mods. Many mods add blocks, item and/or achievements. And every time they (un)install one, their statistics are gone.
Even if you don't care about statistics, your maybe annoyed be the achievement "Taking Inventory" popping up.
KeepMyStats is a simple mod, that removes the resetting of statistics.

Every time the old statistics aren't matching your blocks, items and achievement, Minecraft resets the statistics a sends the message "CHECKSUM MISMATCH" in the console. You see this mod has been working when the next line says "Checksum mismatch ignored."

Screenshot:

Additionally, in a deobfuscated environment (= a development environment), the mod will set the player name to "Player". I a development environment, you always play offline and your username will be different every time you start the game.

Note that statistics are client only. Don't install the mod on a server.

The mod is a FML coremod. This means it requires FML or Forge and goes into the coremods folder. It does not do any Minecraft stuff, so it should be independent of the Minecraft version. It should work with all future releases and snapshots.

Downloads
Installation:
Just copy the files inside the [1.x.x]KeepMyStats.zip into your minecraft.jar and delete the META-INF folder.
The mod doesn't require any other mods.
It is compatible with Minecraft Forge. Install it after Forge.

I have one question, is this forge-compatible? i hate my achievements getting reset, but i got all these forge mods so.. yea lol does it conflict with forge?
EDIT: It IS forge compatible thanks a lot for this mod!

I will be away for 2 weeks, so I can't update to 1.3 soon.
But I could update to 1.3 pre-release. This is probably compatible with 1.3 as well.
Updating a mod without the normal developer tools is complicated and unsafe. The mod might not be 100% bug free. When I'm back, I will release a better version.

This is a great mod and I personally have no idea why Notch made it so stats reset when the Jar is changed. Just another reason why we needed other programmers working on Minecraft to fix Notch's mistakes.